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Determination of cavitation resistance of sintered basalt samples
No full textThe paper examines the cavitation resistance of the sintered basalt samples. A change in the sample mass in function of the cavitation time was monitored for the evaluation of cavitation resistance. The level of degradation of the surface of the sample was quantified using the image analysis. Analyzing the progression of erosion samples of sintered basalt, it can be concluded that the mass loss is small, for 120 min exposure is 2,26 mg, with a cavitation rate of 0.02 mg/min and total surface damage of the sample surface of 15%. It has been shown that sintered basalt samples can be applied in conditions in which high cavitation loads are expected
Cavitation demage morphology of glass-ceramics based on basalt
No full textCavitation is a kind of wear and represents formation, growth and collaps of steam or vapor gas bubbles in a flowing fluid. Collaps of the bubble creates shock waves and micro–jet that are damaging materials in contact with the fluid that flows. It has been shown that the impact formed by collapsing cavitation bubbles cause damage and mass loss of the material, i.e., cavitation erosion. Basalt–based glass ceramics obtained by processes of melting, casting and thermal treatment of the basalt aggregate proved to be suitable for use in conditions of high cavitation loads. The experiment was conducted using an ultrasonic vibration method with stationary sample (ASTM G32 standard). A change in the sample mass in function of the cavitation time was monitored for the evaluation of cavitation resistance. The level of degradation of the sample surface was quantified using the image analysis. The change in the morphology of the sample surface with the test time was followed by scanning electron microscopy. Analyzing the progression of erosion samples of glass-ceramics, it can be concluded that the mass loss is small, for 120 min exposure is 3.53 mg, with a cavitation rate of 0.03 mg/min and total surface damage of the sample of 12%. This technical ceramics shows high resistance to the effect of the cavitation
Efficiency and the possibility of using zeolite and apatite purifying water for irrigation and remedation of contaminated soil
No full textKnowledge of the mobility of heavy metals and radionuclides, such as Pb, Cd, Zn and U, represents one of the goals of protection, regulation, rational use and irrigation of agricultural soils from the aspect of safe food production. The aim of this work was investigation of efficiency of natural mineral materials based on zeolite and apatite from domestic deposits in the mobility of heavy metals and radionuclides in the waters and soils of the different physico-chemical characteristics (pseudogley and chemozem). The affinity, efficiency, zeolite adsorption mechanisms and apatite adsorption precipitation were determined in a constant- pressure column system at 300 mg 1 for different pH values (5.00 and 7.00) of the basic contaminated solution (Pb, Cd, Zn, U) at time intervals of 30, 60, 90, 120, 180 minutes. In all experiments, significant changes in the pH of the filtrate occurred. The most significant changes in the pH of the filtrate, minimal fluctuations in the time interval, at pH = 5.00, recorded the basic solutions of Pb (7.69-7.87) and U (7.77-7.93) during leakage through the column with apatite, while slightly lower changes for Cd and Zn were observed. Changes also occurred in the column with the zeolite, but with a much lower intensity compared to the column of apatite, and with the trend of changes U> Pb Cd Zn. The trend of changes between apatite and zeolite also occurred in the basic contaminated solution with initial pH-7.00. Zeolite and apatite adsorption/precipitation processes successfully immobilized Pb at both tested pH values of stock solution. Our investigation showed that in colonies, apatite better immobilized U, zeolite is better for immobilization of the Cd, while for the Zn both materials showed a very similar affinity. Zeolite and apatite were added in amount of 20 gkg soil to reduce the content of water-soluble and easily accessible forms of Pb, Cd and Zn in uncontaminated and contaminated soil
Nickel removal from aqueous solution using composite based on magnetite/expanded vermiculite
No full textHeavy metal presence in aquatic ecosystems has a huge impact on almost all the living [1]. Problem such as this have to be lessened or eliminated if it is possible. Facile and efficient method for decreasing pollutant concentration from water solutions is by adsorption [2]. In this work raw expanded vermiculite (REV) is utilized as carrier of magnetite microcrystals. This modification of the REV was done by ultrasound and consecutive precipitation of magnetite particles on its surface. This composite is characterized using further methods: X–Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transformed Infra-Red (FTIR), specific surface area (using BET methodology) and Cation Exchange Capacity(CEC) and its adsorption properties are checked. Considering the structure, CEC and specific surface area this material has moderate adsorption parameters. For example, batch adsorption on 35 °C adsorbent accomplished capacity of 19 mg Ni/g and 65.8 % removal of Ni for 90 minutes of adsorption is done on 45 °C are done with S/L ratio of 1,33 g/L. Adsorption kinetics followed pseudo–second order, as exceptedwith equilibrium capacity of 14.27 mg Ni/g and rate constant of sorption of 0.00594 g/(mg min). Isotherm showed the best correlation with Freundlich isotherm model and somewhat poor for Langmuir isotherm. Gibbs free energy decreases with temperature increase showed that the adsorption process is endothermic so chemisorption is the mechanism responsible for nickel removal
Evaluation of urban biotopes – tool for biodiversity protection and sustainable development of cities
No full textCities have a large heterogeneity of habitats (i.e. biotopes) in a relatively small area. Urban biotope
mapping is a procedure for determining and describing the size and distribution of different habitats
(natural and man-made) in the entire urban area with the intention of creating a biotope (habitat)
network. Mapping of urban biotopes and their value assessment is therefore considered to be a
valuable tool for the purpose of sustainable development and preservation of biodiversity in cities.
Methodology for mapping and evaluation of urban biotopes in Serbia was developed for Belgrade
city. Typology for biotope mapping as well as criteria for biotope value assessment were also created.
Actual value of selected i.e. representative biotopes, as well as the potential value of all mapped
biotopes were assessed. Results of biotope mapping are possible to transform for practical use, and
certain recommendations and measures are defined for application in the planning process. So far,
only limited use of these information was noticed for the purpose of urban planning, nature protection
and scientific researches. Thus, there is a need to promote the projects regarding mapping and
evaluation of urban biotopes as a useful tool for biodiversity protection and sustainable development
of cities in Serbia
Development and mechanical properties of the pelletized fly ash
No full textThis paper covers the results of pelletizing fly ash in order to obtain pellets, with satisfied mechanical properties, that can be used in wastewater treatments. Serbian fly ash from “Nikola Tesla” power plant was used as a low cost sorbent. Fly ash was subjected to elementary and XRD analysis. Portland cement was used as a pelletizing agent along with the plastification agent. The mechanical properties of pellets were investigated using different methods such as: pressure resistance, impact resistance, resistance to abrasion, and disintegration in water. The best results were obtained with the addition of 10 % of cement along with the plasticizer
Investigation of the flotation parameters for the ore from ’’Cerovo – C2’’ deposit – cementation zone
No full textThe part of the results, obtained during the technological investigations of the ore
from the deposit ’’Cerovo-C2’’ deposit - Cementation zone, are presented in this paper.
Investigations were undertaken at different flotation conditions (three collectors and grinding
fineness) in order to define possibility and optimal conditions for processing the ore from this
deposit. Obtained results indicate the possibility for producing the copper concentrate with the
commercial quality. Best results were obtained with the collector Flomin C4132 and grinding
fineness of 80 % below 0.074 mm, where the copper content in the rough concentrate was 4.64 %
and the copper recovery was 81.74 %
Uklanjanje kadmijuma biosorbentom na bazi kukuruzne svile iz vodenih rastvora
No full textU ovom radu ispitana je upotreba kukuruzne svile za uklanjanje kadmijuma iz vodenih rastvora i to: sintetičkih rastvora i kontaminirane otpadne vode koja nastaje nakon procesa analize na Atomskom Apsorpcionom Spektrofotometru (AAS). Biosorpcioni eksperimenti su vršeni u šaržnom sistemu. Karakterizacija kukuruzne svile pre i nakon procesa biosorpcije kadmijuma vršena je ATR-FTIR i TGA/DTA tehnikama. Eksperimentalni rezultati ukazuju da kukuruzna svila za uklanjanje kadmijuma i drugih teških metala iz realne AAS otpadne vode potvrđujeda se ovaj materijal može koristiti kao efikasan i jeftin biosorbent
Biosorption of copper by immobilized Myriophyllum spicatum
No full textBiosorption removes pollutants such as heavy metals onto a natural adsorbent, so it can be considered as a promising method of water purification. The objectives of this research were to examine the application of aquatic weed Myriophyllum spicatum immobilized in alginate beads – MsA for the removal of copper from aqueous solutions. Appield biosorbent was characterized by Fourier transform infrared spectroscopy (FT-IR). Experimental results were fitted by six isotherm models, and have showed that MsA holds great potential for copper removal, q = 1.307 mmol/ Results of TOC analyses showed that after Myriophyllum spicatum immobilization process , total organic carbon in MsA was more than four times less than with aquatic weed M. spicatum, 18.8 mg/L compared to 81.2 mg/L of TOC
Thermal and Mechanical Behavior of Composite Mortars Containing Natural Sorptive Clays and Fly Ash
No full textMineral additives are extensively applied as cement replacement materials in both construction concrete and mortar. Fly ash is one of the most commonly utilized additives which improve Theological properties, as well as thermal and mechanical behavior of mortar, and as such it has been widely investigated. This industrial byproduct comprises heavy metals in its composition; therefore further research is needed to optimize its effective dosage. Moreover, certain sorptive clays, such as natural zeolite and bentonite, can prevent migration of toxic elements from fly ash by immobilizing them in their structure. Ten experimental mortars are prepared with Portland cement, river sand and addition of fly ash, zeolite and/or bentonite in accordance with chemometric experimental design rules. The aim of the study was to investigate the effect of mineral additives on thermal and mechanical performances of mortar. Thermal characteristics were monitored via dilatometric analysis and DTA method. Principal component analysis was used on the results of physico-mechanical testing (workability, bulk density, water absorption, shrinkage, compressive and flexural strength) to enable the divisions of the observed samples into groups in the factor space. The performance of Artificial Neural Network was compared with the experimental data in order to develop rapid and accurate method for prediction of mechanical parameters of mortar. The ANN model showed high overall prediction accuracy (r(2) = 0.989, during training cycle). The test results indicate that incorporation of the mineral additives gave cost effective mortars with sufficiently good properties. However, tools of analytical modeling highlighted mortar with zeolite and fly ash as the optimal composition regarding its mechanical performance